In the textile machine industry different embodiments of production machines have been known for a long time in which yarn balloons are formed during operation in the region of their often numerous workstations or associated operating devices.
Such production machines therefore have monitoring devices for determining and limiting the size of said yarn balloon, which can operate in very different ways. The known monitoring devices often have optical sensor devices for example, by means of which the rotating yarn that forms the yarn balloon is observed.
In German Patent Publication DE 101 03 892 A1 for example a method and a device are described by means of which the yarn take-off speed of feed bobbins arranged in the creel of a beaming machine is optimised.
It is known that when a yarn is drawn off a feed bobbin, which is positioned in an associated creel during the operating process overhead and at a relatively high take-off speed, a yarn balloon is formed, the diameter of which is dependent on the yarn take-off speed. The size of the yarn balloon thus increases with increasing yarn take-off speed.
In the method known from German Patent Publication DE 101 03 892 A1 by means of measuring means arranged on the creel the size of at least some of the yarn balloons created during the yarn take off is determined and transmitted to a control device, which when reaching limit values of the yarn balloon ensures that the yarn take-off speed is controlled by intervention.
As measuring means for determining the yarn balloon size various different optically operating measuring units are used, for example a camera, one or more light barriers or similar devices.
Optically operating measuring devices for detecting a yarn balloon form and/or a yarn balloon size are known from German Patent Publication DE 22 55 663 A1 and European Patent Publication EP 0 282 745 A1 also in connection with ring spinning machines.
In German Patent Publication DE 22 55 663 A1 for example a workstation of a ring spinning machine is described which is equipped with an air or magnet-mounted spinning ring, on which a spinning rotor runs driven by the running yarn.
As during the operation of such workstations, in order to ensure a perfect spinning process, it is known that it is necessary to have a specific difference between the speed of the spinning ring and the speed of the spinning rotor, during the spinning operation both the speed of the air or magnet mounted spinning ring and also the speed of the spinning rotor is controlled.
Furthermore, in this method there is continuous monitoring of whether a predefined maximum yarn tension is being maintained and the yarn balloon forming during the spinning in the region of the spinning cop is controlled and also stabilised. This means that by measuring the deviation of the yarn curve of the yarn balloon from its meridian plane and adjusting the yarn tension accordingly by means of variably braking the spinning ring, the course of the yarn curve of the yarn balloon is stabilised. The device for detecting the deviation in the yarn curve of the yarn balloon consists essentially of a measuring sensor which comprises a series of small photoelements as well as a trigger device which ensures that the yarn balloon is periodically flashed.
The known devices are either (German Patent Publication DE 22 55 663 A1) relatively complicated and often very inaccurate or because of their large measurement range (German Patent Publication DE 101 03 892 A1) are often very sensitive to air pollution.
Therefore in practice these known devices have not won general acceptance.
European Patent Publication EP 0 282 745 A1 describes a method and a device for monitoring the production and quality of the workstations of a multi-spindle textile machine.
This means that a ring spinning machine is equipped with an optical monitoring element, which simultaneously checks a plurality of workstations of the textile machine arranged next to one another in series in that the yarn balloons rotating in the region of the workstation are illuminated.
The monitoring element comprises for this purpose a transmitter and a receiver, which are designed and arranged so that a beam bundle sent by a transmitter on route to a receiver passes through the numerous, rotating yarn balloons and is interrupted or weakened intermittently by the yarn balloons.
The shadow is converted in the receiver into an electric signal which is used in an associated control device as the basis for further evaluation.
Also the method described in European Patent Publication EP 0 282 745 A1 is occasionally very inaccurate as the beam bundle is often influenced negatively on route from the transmitter to the receiver by dust and fibre particles which are almost impossible to avoid in the atmosphere of a spinning room.
Furthermore, by means of European Patent Publication EP 2 419 554 B1 a workstation of a two-for-one twisting and cabling machine is known, the spooling and winding device of which is arranged so that during operation it lies inside a yarn balloon.
In order to check the size of the yarn balloon the workstation has a monitoring device which can have various different embodiments.
The size of the yarn balloon can be determined for example by a yarn tension sensor, which is arranged either between a yarn drive device and the inlet of the yarn into a spindle, which ensures the formation of the yarn balloon or by means of a yarn tension sensor, which is positioned between the outlet of the yarn from the spindle and an additional yarn drive device.
In a further embodiment it is possible to detect the size of the yarn balloon and also measure the output or torque of the drive device of the spindle. This means that by means of a measuring device the power is determined which is received by the spindle drive and from this the size of the yarn balloon can be determined in an evaluation device.
From European Patent Publication EP 2 419 554 B1 also the use of different optical measuring devices is known which monitor the yarn balloon rotating around the spooling and winding device.
In a first embodiment for example the use of a light barrier is proposed which has a light source for emitting a light beam and a light-sensitive detector for picking up the light beam.
In a comparable, second embodiment a type CCD light sensor is used in connection with a beam-like, stroboscope light source, for example LED or laser.
In the device which operates with a light barrier, during operation the interruption of the light beam is identified by the yarn of the yarn balloon running past.
In the device which acts with a light sensor and a stroboscopic light source, which is synchronised with the rotation of the spindle, the image and thereby the form of the yarn forming the yarn balloon is localised when it is lit up by a flash.
The various different monitoring devices described in European Patent Publication EP 2 419 554 B1 in connection with a workstation of a two-for-one twisting and cabling machine can also be improved upon, as they either do not take accurate enough measurements or are also relatively sensitive to dirt.